1. Field of the Invention
The present invention relates to a sheet member feeding device for intermittently feeding a sheet member for a predetermined amount, a recording apparatus employing the same, and an image pick-up apparatus with the recording mechanism employing the same.
2. Description of Prior Art
In a recording apparatus, such as a printer or the like, a feeding device for intermittently feeding a printing medium for a predetermined feeding amount across a recording portion for forming a desired image on the printing medium, is provided in a feeding passage of the printing medium. The feeding device is primarily constructed with a feeding roller unit for feeding the printing medium while pinching the printing medium, a driving motor for supplying a driving force for the feeding roller unit and a speed reduction mechanism portion for transmitting the driving force of the driving motor to the feeding roller unit at a reduced predetermined speed, for example.
The feeding roller unit is arranged at an upstream portion of a recording portion in the feeding path and extends substantially perpendicular to a feeding direction of the printing medium. The feeding roller unit is driven intermittently per a predetermined rotational angle according to the progress of a printing operation. Angular displacement of the feeding roller unit per one time corresponds to a feeding amount of the printing medium per one time and is set depending upon the mode or speed of the recording operation of the recording portion. At this time, relatively high precision of the feeding amount of the printing medium per one time is required. In particular, in order to increase the resolution of the image to be formed on the printing medium so as to achieve relatively high resolution and increase feeding amount of the printing medium at one time, image degradation including white lines and dark lines due to error of feeding amount can be formed on the basis of error in the feeding amount. Thus, relatively high precision of feeding amount is required for avoiding degradation of printed image quality. For this reason, it is required to make an error in angular displacement of the feeding roller unit at one time relative to a predetermined reference angle relatively small.
As the driving motor is a stepping motor or a DC motor, for example, the number of output revolutions thereof is relatively high, and the output torque is relatively small. Therefore, a driving force of the driving motor is supplied to the feeding roller unit with a reduction of rotation speed and an increase in torque by the speed reduction mechanism portion, as discussed above.
The speed reduction mechanism portion is constructed with a gear train having a predetermined gear ratio, for example.
When a driving force from the driving motor is intermittently transmitted to the feeding roller unit via the speed reduction mechanism, error in the feeding amount of the printing medium by the feeding roller unit is cumulative of machining precision of respective gears in a power transmission path including the driving motor, the speed reduction mechanism portion and the feeding roller unit, such as tolerance in precision of tooth space run-out of respective gears, for example.
However, in order to further enhance precision in the feeding amount, since there is a limitation in improving precision of tooth space run-out of the gear, error in the rotation angle of the feeding roller unit relative to the predetermined reference angle due to accumulated tolerance in machining respective gears, namely error in the feeding amount of the printing medium by the feeding roller unit, is still caused. Also, when machining precision of respective gears is the same class of accuracy of machining each other, the smaller the modules of the gear that make up the speed reduction mechanism portion due to demand for down-sizing of the recording apparatus becomes, the greater the tooth space run-out in the smaller diameter gear tends to become. Therefore, error in the feeding amount of the recording medium in the feeding roller unit becomes large.
The present invention has been worked out in view of the drawbacks in the prior art. The present invention relates to a sheet member feeding device for intermittently feeding a sheet member for a predetermined amount, a recording apparatus employing the same, and an image pick-up apparatus with the recording mechanism employing the same. It is an object of the present invention to provide a sheet feeding device which can reduce variations of error in feeding amount of a sheet member to be fed due to tooth space run-out of a gear irrespective of the maximum and the minimum of the module of the gear, a recording apparatus employing the same, and an image pick-up apparatus with a recording mechanism including the recording apparatus.
In a first aspect of the present invention, there is provided a sheet member feeding device comprising:
a first gear transmitting a driving force to a feeding roller for intermittently feeding a sheet member per a predetermined feeding amount;
a second gear having a first mark and a second mark representative of a maximum eccentric position and a minimum eccentric position along a radial direction relative to a predetermined concentric circle in tooth space, in opposition to each other, and directly or indirectly transmitting a driving force to the first gear;
a third gear directly or indirectly transmitting driving force from driving means to the second gear;
detecting means for detecting the first mark and the second mark in the second gear and transmitting a detection output; and
a control portion operating the driving means so as to rotate the second gear through 180xc2x0 between the first mark and the second mark with respect to feeding for a feeding amount of the sheet member for one time, on the basis of the detection output from the detecting means.
In a second aspect of the present invention, there is provided a printing apparatus comprising:
a sheet member feeding device;
a printing portion performing a printing operation on a surface of a sheet member intermittently fed by the sheet member feeding device; and
a control portion performing operation control of the printing portion.
In a third aspect of the present invention, there is provided an image pick-up apparatus with a printing mechanism comprising a printing apparatus and an image pick-up mechanism.
As will be clear from the discussion hereabove, the sheet member feeding device, the printing apparatus employing the same and the image pick-up device having a printing mechanism according to the present invention, are provided with a first gear transmitting a driving force to a feeding roller for intermittently feeding a sheet member per a predetermined feeding amount, a second gear having a first mark and a second mark representative of a maximum eccentric position and a minimum eccentric position along a radial direction relative to a predetermined concentric circle in tooth space, in opposition to each other, and directly or indirectly transmitting a driving force to the first gear, a third gear directly or indirectly transmitting driving force from driving means to the second gear, and detecting means for detecting the first mark and the second mark in the second gear and transmitting a detection output. The control portion operates the driving means so as to rotate the second gear over 180xc2x0 between the first mark and the second mark with respect to feeding for a feeding amount of the sheet member for one time, on the basis of the detection output from the detecting means for reducing variations of error of feeding amount of the sheet due to tooth space run-out of the gear without depending upon large and small of the module of the gear.
The above and other objects, effects, features and advantages of the present invention will become more apparent from the following description of embodiments thereof taken in conjunction with the accompanying drawings.